Usless Mechatronics
by demonwolfkid
Summary: Zombies AU: This wasn't his world, it couldn't be. He isn't alive. He died. Right? He can't be here. He can't be alive. It's not possible.
1. Chapter 1

Idea stemmed from the oneshot Pythagorean Theorem by WookieCookie, so read that first so this'll make sense.

Also, I don't own BH6

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At one point while hanging out after school in the lab they'd jokingly brought up the subject of a zombie apocalypse.

It wasn't anything serious, Hiro didn't actually know where the conversation had started, he'd walked out to get some more supplies and walked in on an argument.

The subject? Who would survive?

He wished that they could still joke about that, that his life hadn't turned into the clusterfuck of he didn't even know what.

He was a science guy, a leading name in robotics and probably, if not certainly, the youngest person in his field.

And yet, he'd never expected this.

Nobody could fault him for that though, what this was was purely in the realm of science fiction, but then again, so was turning Fred into a fire breathing monster and look what happened.

He can't bring himself to accept it.

And yet…

He's here.

Not his him, no, it wasn't _his_ Tadashi, but it was _Tadashi._

He'd never missed his parents, not for a lack of trying, but he just didn't remember them. Tadashi is- was his only family, the only person he could count on. Sure, he had Aunt Cass but there had always been a certain awkwardness, sure, it'd gotten better over time, especially in the wake of Tadashi's death, but it was still _there._

"Hiro, you okay?"

This Tadashi has his voice, his face, but not his past. He'd learned about him over the weeks, speaking so rarely that he knew this Tadashi was worried. He tried, but he couldn't bring himself to get too close, as a crime fighter, and more so as Hiro Hamada, he knew what death was. He had enough self-preservation to stay away, especially in this world.

"I'm fine."

There were moments though, when they were boarded up inside a house, safe –for the moment– from the outside world, when Tadashi would sit next to him and just talk, because this Tadashi hated silence like no other. He'd talk about ten years ago, about before the zombies. When Hiro asked about Aunt Cass Tadashi changed the subject –this Tadashi was really good at that. His Tadashi never had anything he needed to hide.

Tadashi didn't look like he believed him, but went to check the fortifications

It had been ten years. Apparently they'd lived in the San Fransokoyo safety zone for the vast majority of the time, until the area was deemed infected and the military bombed their safe haven. Since then they'd been on the run. The Fireflies were an extremist group, of a sorts. He wasn't quite sure what to think of them, he didn't have quite enough information just yet.

He missed the others. GoGo and her fast-talking, quick-thinking, iron clad wit and sharp as daggers tongue. Wasabi ad his true, actual OCD who would count every single one of his tools before he left the lab. Honey Lemon and her optimistic, never look back attitude, and Fred, the easy going idiot who wasn't actually an idiot.

"You sure you're okay?"

He'd asked, but this Tadashi didn't know them, not even by their real names.

"I'm fine."

His knees were up to his chest and he grimaced. This Tadashi was much more perceptive than his Tadashi, not that Tadashi was oblivious or anything.

"Hiro…"

"I said I was fine!" he stood up, his brow furrowed. Why couldn't this guy leave him alone? He wasn't actually his brother. They weren't family. He was just a stranger with his brother's face.

He stormed away before the more rational part of his brain could take over.

He wasn't his brother, he wasn't his Tadashi. This _person_ was a stranger. He could die to those- those _things_ for all he cared.

He wasn't Tadashi…

He wasn't.

He missed Baymax, but if Tadashi didn't know the others then there was no way Baymax existed, and even if he did, there was no guarantee that it would be _his_ Baymax.

He pressed his head up against the wall, pealing plaster met his forehead as tears dripped down his nose.

No, he wasn't crying. He couldn't cry. He'd already lost Tadashi, the others weren't here, they were alive, back in his world. This _place_ wasn't his. It didn't matter what happened to them. It wasn't his problem.

So what if he was the solution, the kid that was immune.

Damn it.

He punched the wall, his hand unfolding as tears streamed down his cheeks.

He couldn't do that! Not after everything... They'd find a cure! They had to!

This wasn't his world.

It'd been ten years! It was only a matter of time!

"Hiro?"

He froze. Tadashi must've heard him punch the wall. Of course he heard him punch the wall. It was absolutely silent otherwise.

Quickly he whipped his face, retreating into one of the rooms he'd scouted out earlier to glance in the mirror.

Did he look like he'd been crying? There was less dirt on his face, and the dirt that was there was smudged awkwardly. Rubbing his cheeks with his hand he heard the telltale creaks of the floorboards as Tadashi made his way up the stairs.

"Hiro? You okay?"

Damn it. Damn it. Damnit! DAMNIT!

NO!

He wouldn't be weak!

He wouldn't!

He glanced at himself again, deeming the dirt properly smudged. With a quick glance around he began rummaging through the various cabinets, hoping to find something to excuse his being up there.

Did he need an excuse? Obviously he'd been angry. At what he couldn't even pinpoint, let alone explain to this- this stranger.

"What are you doing you knucklehead?"

Hiro scowled

_Knucklehead. Knucklehead. Knucklehead._

No. This wasn't Tadashi. It wasn't his Tadashi.

"Tch," he brushed past him, leaving a bewildered Tadashi in his wake.

He didn't need to get close to this person, not in a world so filed with death. Everyone died. It was a fact of life, and this world had a lot more death than life it seemed

He could deal with this world. He could deal with this life, but he'd really rather not have to deal with loosing another Tadashi.

It was surprisingly easy, to act like he didn't care.

He didn't. He couldn't.


	2. Chapter 2

Over the past week he'd gotten used to running.

Running was easy, mindless. Tadashi seemed to know all the ins and outs, or at least he was able to find them easily enough.

Nine days. He'd been in this world for nine days.

He'd gotten really good at running.

"Hiro, talk to me."

It was also seven days since Hiro had taken his vow of silence, as he jokingly liked to think of it. He only answered when he had to, only spoke when he needed to.

It was getting to Tadashi. Really getting to him.

"Hiro."

"I told you, I'm fine."

He probably wasn't. Baymax would probably diagnose with weird mental disorder, probably schizophrenia. That'd be hilarious.

He'd do anything to hear the robots voice. The echoy metallic voice. Baymax had been his constant companion for the last year and a half, a remembrance, but more than that, Baymax was his best friend.

"No. You're not."

Hiro looked up with trepidation as he saw the look in his brother's eyes. Something between sternness, and concern.

The depth of the pain. It was like back when they were in middle school, when he'd gotten a case of leukemia, the overwhelming concern that he gleamed from just that look.

He couldn't keep his gaze, choosing instead to look at his feet. The sneakers that they'd found three safe houses before this one were caked in blood. Real, human blood.

Tadashi didn't kill.

It was so _wrong._

"I'm fine."

Tadashi let out a groan of frustration, leaning his back against the wall and looking up at the sky.

Hiro sneaked a glance at them and swallowed.

He didn't owe this Tadashi anything. He didn't have to say anything.

"Hiro. Talk to me," his voice broke and Hiro sank his chin into his knees letting his bangs fall over his eyes, ignoring the way this person bent to try to look at him, ignoring the arm that snaked its way around his shoulders as he was pulled closer to him. The way his hair moved as Tadashi leaned his head atop his own like he used to when they were little. "Talk to me bro."

It wasn't him.

The building creaked, and not for the first time Hiro wondered about the wisdom of staying locked up in a mall of all places.

"It's fine little brother," Tadashi said, as if out of reflex, as he turned his worried gaze to him. "It's fine."

He made a move to stand up and Hiro let out a quick, panicked breath.

"Where you going?" he asked, scrambling to stand himself. "Tadashi!"

"Shh!" that wasn't Tadashi, but it was. The worry, the seriousness, but he smiled that stupid crooked smile of his and reached out to ruffle his hair. "Don't worry, punk, I'll be right back."

Yeah, but you're not the one with the immunity.

"Be careful." It was out of his throat before he could stop it, but he found he wasn't disappointed that he said it. He'd never gotten to say goodbye to Tadashi.

Tadashi looked surprised, blinking momentarily before giving him a nod and a quick smile. "Aren't I always?"

And he was, he was the careful one, the one who was always careful. And yet he was the one who died.

Fear gripped the fifteen year olds heart as he watched Tadashi lift up the metal gate, shimmying his body through gap in the interwoven metal.

No. He couldn't die. He didn't care if he wasn't his Tadashi, Tadashi couldn't die. He couldn't!


End file.
